Catalytic Converter question

My dads car just failed it's MOT... failed on the exaust and Catalytic Converter.. I'm just wondering if a catalyic converter from a standard ford fiesta, or a ford fiesta mk3 catalytic converter would work with a ford fiesta SI?. My dad says it won't but I have a feeling it might as it's still a fiesta..

All depends when the car was first manufactured/homologated. I think 1990 is the cut off era (someone shout if that's wrong!), anything designed before then doesn't need a cat.

*shouts*

well ok, I'm not 100%

I believe 1995 is the point by which all cars HAD to have a converter.

I've seen some debate as to how cars with cats before that can be treated, if anyone's got the MOT handbook and can quote exactly what it says about cars made with cats before they where compulsory.

Here's my take on it:

Unfortunatly I'm not 100% on what Fraud where doing at that stage but I *think* they might possibly have all had cats by then (I'll go check with the sales gumph in a bit). It may be the case that your MOT tester is checking to see if it requires a test in the book. It MAY be they saw the cat on it and tested it (it has to work if it's fitted, no matter the date).

What I'm going to say is this. If a tester didn't see the cat, what's to say it's a catted engine? There's a great deal of MK3 fiestas out there without. OK, there's a couple of clues, it's a CFi unit rather than a carb and a HEGO stuck in the downpipe. Depends on the garage.

Unless the engine code's clearly visable. Mine was a sticker on the front of the timing chain cover apparently.... think that's survived since 92?

Cats cost a lot. It could be a sensor problem causeing the EEC-IV to fuel wrong, but, more likely the cat's on the way out. They're expensive items. I suggest you have a friendly conversation with MOT stations as to where they'd stand on it uncatted.

Saying that though, it's not illegal to run without a cat. There's no law that states you MUST have a cat. You'll probably fail an emmissions test without one unless your engine is running spot on, but it's not a legal requirement.

Saying that though, it's not illegal to run without a cat. There's no law that states you MUST have a cat. You'll probably fail an emmissions test without one unless your engine is running spot on, but it's not a legal requirement.

K and L plate motors without cats? Such as? I can only imagine they were old cars registered a lot, lot later down the line to get away with that.

9th November 2003

The aim of the catalytic converter is to dramatically reduce the three most harmful exhaust emissions — carbon monoxide, hydrocarbons and nitrogen oxides — hence the term “three-way catalytic converter”. The device is required on unleaded petrol-engine passenger cars first used on and after 1 August 1992.

It’s called a converter because the emissions that go into the catalyst are converted to more benign substances such as carbon dioxide, nitrogen and water vapour. The device is fitted in the exhaust system just under the driver or passenger footwell and looks like a conventional silencer box, albeit flatter and squarer.

The converter has two sections: a reduction catalyst and an oxidisation catalyst. Each is made of a ceramic honeycomb with a metal coating. The honeycombs create the maximum surface area for exhaust gas to pass over.

Inside the reduction catalyst, the honeycomb is coated with platinum and rhodium, which are used to reduce nitrogen oxides in emissions. As the gas passes over the platinum and rhodium, a chemical reaction takes place that splits the nitrogen atoms from the oxygen. Both are harmless in their separate forms.

In the second stage, hydrocarbons (from fuel) that have passed unburnt through the engine, together with carbon monoxide, are oxidised (burnt, basically) on a catalyst coated with platinum and palladium.

It is because so many rare and precious metals are used that a replacement converter costs so much (between £100 and £500) but without it, your car will not pass the MoT test. Eventually, a converter will wear out (three to four years would be typical), though it can be physically damaged by knocking it on a kerb, or by an engine backfire. Mistaken use of leaded petrol will also ruin a converter.

Mk2 CRX VTEC cars all came with CATs, as did the EDM models with the D16A8 non-VTEC engine. However they will all pass the MOT without a cat due to when they were made

If your car has a CAT and you take it out, make sure you know how it will affect the engine management. If there's an O2 sensor after the CAT in the exhaust, it will probably switch into 'limp home mode' unless you fake the sensor reading or remap the ECU.